Duct-forming devices



April 12, 1966 s. M. ZANDMER DUCT-FORMING DEVICES 2 Sheets-Sheet 1 Filed May 23. 1961 April l2, 1966 s. M. ZANDMER DUCT-FORMING DEVICES Filed May 25. 1961 2 Sheets-Sheet 2 as. 9e J 4 United States Patent O 3,245,472 DUCT-FORMING DEVICES Solis Myron Zandmer, Banff, Alberta, Canada Filed May 23, 1961, Ser. No. 128,609 2 Claims. (Cl. 166-100) This invention relates to apparatus for providing ducts or passageways for the flow of uids between selected earth strata and the interior of a borehole casing or liner.

Until recently, bore hole casings or liners have been set in drilled bore holes by a cementing process in which fluid cement is forced down through the casing and then upwardly around the outside of the casing. The cement fills the annular space between the outside of the casing or liner and the surrounding earth or formation through which the drilled bore hole extends. It has then been customary to preforate the casing or liner and the surrounding cement at the level or levels of producing strata by means of shaped charges (jet perforators) or by means of gun-type perforators which force projectiles through the casing or liner and the cement to form passageways or ducts therethrough. Such known methods and apparatus produce various difficulties such as (l) a shattering of the cement seal; (2) the destruction of the sealing bond between the casing or liner and the cement and between the cement and the surface of the bore hole; and (3) the formation of cracks in the cement; all of which make the cement subject to destructive attack by acids subsequently used for the purpose of acidizing the oil-bearing strata to increase the ow of fluids from such productive strata, and may allow acids or other production stimulating materials to leak or flow from a less permeable stratum to a more permeable stratum (when applying pressure selectively at other given bands or areas of perforations) through cracks in the cement formed by the effects of explosive previously used.

It is an object of the present invention to provide im proved `apparatus for forming a duct or passageway through the bore hole casing or liner and the surrounding cement seal in order to establish communication between a selected producing stratum and the interior of the casing or liner.

It is another object to provide a duct-forming device which includes a single sleeve, or two or more relatively telescoped sleeves, moved by fluid pressure within the casing toward the wall of the bore hole when such sleeves are released, the single sleeve, or the inner of the two or more sleeves being adapted to Vengage the bore wall withV such impact as to pierce through any coating or film of drilling debris caked on the surface of the bore wall.

It is another -object to provide a duct-forming device which includes one or more sleeves movable outwardly when released, and forming a longitudinal passage which is closed preferably by two diaphragms and a check valve preferably interposed between the two diaphragms; the diaphragms being punctured by a fluid under pressure greatly in excess of that required to release the sleeves, or removed by chemicals or by electrolytic action.

It is another object to provide a duct-forming device of the kind r'irst briefly described wherein the passage is formed by aligned, bored plugs of chemically-dissolvable material held within the sleeve, or within the inner of the telescoping sleeves if more than one sleeve is used.

In the accompanying drawings, wherein is shown the preferred form of the invention,

FIGURE 1 is a vertical section, more or less diagrammatic, of a bore hole provided with a casing sealed in the formation and indicating the location of duct-forming devices according to this invention;

FIGURE 2 is an enlarged horizontal section showing one of the duct-forming devices, initial position, before ICC being extended to engage a producing stratum, and before the sealing cement is placed in position;

FIGURE 3 is a view, partly in vertical section and partly in elevation, of the device in extended position;

FIGURE 4 is an enlarged fragmentary section of the duct-forming device; and

FIGURE 5 is a perspective view of the duct-forming device, mounted in a guard.

Referring to the drawings for the purpose of illustration, a bore hole 10 is drilled in the earth .11 by any conventional dn'lling apparatus. In drilling a bore through limestone formations, for example, the bore hole 10 may be of approximately 9 to l0" in diameter and will have a relatively smooth but irregular surface. A bore hole casing or liner 12 is positioned in the bore hole 1li; it may be formed of steel tubing of about 51/2" or 7" outside diameter. Thus, an annular space about 1" to 11/2 is provided between the outer surface of the casing or liner 12 and the wall of the bore hole 10. The casing or liner 12 is sealed to or set in the formation 11 by means of cement 13. The cement 13 may be Portland cement or any other composition or settable material not adversely affected by oil, gas, or bore hole treating chemicals.

Oil and gas zones usually have a plurality of oil or gasproducing bands or strata, indicated by the numeral .14. Some of the strata 14 may be more porous than other adjacent strata. The porosity or permeability of the individual strata may be determined by analysis of specimen cores or by electrical testing apparatus; the degree of permeability is usually expressed, in the United States of America and Canada, in terms -of millidarcies. Where a bore hole traverses several strata of different permeabilities and the strata are to be stimulated, that is, treated by acids or other chemicals (or, as is practised in America, by Fac-ing), it is desirable that the cement seal 13 be maintained unbroken so that upon the application of treating materials or acids under pressure there will be no leakage outside of the casing 12 from one stratum 14 to another stratum 14 of greater permeability. In actual practice, the strata 14 may be found to be of small thickness and possibly spaced only a few feet apart vertically.

The casing `or liner 12 is provided, before its introduction into the bore hole, with a plurality of vduct-forming devices, made according to this invention, indicated by theV numeral 15, disposed along the casing or liner 12 at levels to correspond with the levels of the strata 14 to be treated and tapped; or, if preferred, the ductforming devices may be arranged in a certain pattern,

so that there may be so many devices per stratum acy cording to its thickness.

Such a duct-forming device will now be described, first with reference to its original position, as shown in FIG- URE 2. It is preferable to mount the duct-forming device in a ring or guard G having a curved surface S Welded to the outer surface of the casing or liner 12. The device hole and tend to center it. The bore of the guard is centrally located with respect to the axis of an opening 40A in the casing or liner 12. It is provided with internal threads 17, and a shoulder 1S which is adapted to be engaged by the bushing 16 `of the device when the bushing is threaded into the bore of the guard.

A suitable O ring (a gasket) 56 housed in a groove formed in the bushing (see FIGURE 2) serves to pro-V vide a fluid-tight connection between the bushing and the guard. The bushing 16 has recesses 22 for the application of a wrench to tighten the duct-forming device in the mounting guard G.

The surface of the bore of the bushing 16 is provided with a plurality of annular grooves 31, forming a serrated inner surface. The grooves present forward frusto-conical surfaces T (see FIGURE 4) inclined downwardly toward the outer end of the device, and rearward surfaces R substantially perpendicular to the axis of the device.

A sleeve Z1, formed with an enlarged rear portion 37 (see FIGURE 4) having an annular groove 39 in its outer surface near its inner end, is slidably mounted within the bushing 16. The groove 39 is in part deiined by a surface X (see FIGURE 4) inclined to the vertical and directed upwardly toward the outer end of the device. A split spring ring 32 is carried in groove 39 and, under tension, normally engages in one of the grooves 31 of the bushing 16, contracting and riding successively over the inclined frusto-conical surfaces T of such grooves 31 as the sleeve 21 is moved outwardly in the bushing 16. On the other hand, if the sleeve tends to move inwardly in the bushing, the inclined cam surface X of the groove 39 exerts a force on the ring 32 upwardly and rearwardly, normal to the cam surface and the sleeve is thus prevented from moving inwardly in the bushing. The split ring 32 thus serves as a locking member preventing rearward (inward) movement of the sleeve in the bushing after the sleeve has moved outwardly in the bushing.

The outer sleeve 21 is formed with a rectangular groove 30 adjacent its inward (rear) end. In the groove is seated a split ring like wire 104i of square or rectangular cross section. In practice, the wire is made of magnesium. The wire bears against a shoulder formed into the bushing, so that the sleeve is prevented from moving outwardly in the bushing until the wire is sheared ott. It has been found that a wire of square or rectangular cross section is greatly more satisfactory than a wire of circular cross section, in that its shearing strength for a given width (thickness) and given composition, does not vary in practice. A wire of circular cross section, on the other hand, since it will not always shear exactly along its exact longitudinal center, did vary considerably in its shearing strength. Also, by using such a shear device, that is, a length of wire formed into the shape of a split ring the required shearing strength can be easily computed since it is, for a given composition, and a selected thickness, a measure of the length of the wire. In practice the wires 100 will shear, to release the sleeves, when the fluid pressure within the casing 12 is between 1500 and 180() pounds per square inch.

The outward movement of the sleeve 21 in the hushing 16 .is determined (arrested) by the engagement of the enlarged portion or shoulder 37 with the inner end of the plain or iungrooved front bore portion of the bushing 16 (see FIGURE 3).

The bushing 16 is provided with a groove containing an O-ring 34 engaging the outer surface of the sleeve 21 to `form a pressure seal between the bushing and the sleeve.

The sleeve 21 has its inner bore provided with a plurality of annular grooves 36 similar to the grooves 31 of the bushing 16.

An inner sleeve 40 is slidably mounted within the sleeve 21. The sleeve 40 is provided with a groove 39A similar to the groove 39 of the bushing 16, and a split spring ring 32A. This ring also serves as a locking member preventing inward movement of the sleeve 40 in the sleeve 21.

The sleeve 40 is also formed with a rectangular groove 30A adjacent its inward (rear) end in which is seated a length of wire 100A of square or rectangular cross section for the purpose served by the wire 166 and groove 30 aforesaid, that is, to free the sleeve 40 for outward movement relatively to the sleeve 21 as the wire shears 4 upon application of a predetermined uid pressure within the casing.

The sleeve 21 is provided with a groove in which is an O-ring 37A to engage the outer surface of the sleeve 40 to provide a uid-tight seal.

The outward movement of the sleeve 40 within the sleeve 21 is determined (arrested) by the engagement of the raised portion 37B of t-he sleeve 40 with the inner end of the plain or ungrooved front bore of the outer sleeve 21 (see FIGURE 3).

The outer sleeve 21 and the inner sleeve 40 are provided with channels 48. Thus, communication passages are provided between the annular space between the bushing 16 and the outer sleeve 21, and the annular space between the two sleeves 21 and 40, and atmosphere, such passages forming exits for grease or other suitable compound packed in the annular spaces as the outer sleeve moves outwardly within the bushing and as the inner sleeve moves outwardly within the -outer sleeve.

The compound is used to protect the acid-soluble parts of the device before it is used. It may comprise sweet glycerine and powdered limestone.

Applied to the inner (rear) end of the device, more particularly to the bushing 16, is a thin metal cap 25, of magnesium. The cap may be one which is snapped on. In practice, the cap has a small orice. The cap provides a closure for the inner end of the device.

Threaded into the inner end of the sleeve 40 is a tubular plug 43; threaded into the outer end of the sleeve is a tubular screw 62. Disposed in the sleeve between the screws 43 and 62 is a valve body 47. Also disposed in the sleeve, to be engaged by one (the left-hand) end of the valve body is a perforated disc or wafer 64. Pressed by and between the screw 43 and the valve body 47 is a thin diaphragm 57, of zinc. Pressed by and between the wafer 64 and the screw 62 is another diaphragm 61, of magnesium. Inserted and held within the bore of the screw 43, say by friction, is a plug 45, of magnesium. Also inserted within the bore of the screw 62 is a plug S9, of magnesium. As is known, magnesium is readily soluble in acetic acid; zinc is not.

As shown, the plug 59 is formed to protrude beyond the outer end of the sleeve 40 so as to engage the well bore surface without being so prevented by the engagement of the sleeve with the bore surface. Thus, the plug will pierce any coating or lm or drilling debris on the bore wall before the inner sleeve 40 engages the wall.

To insure Huid-tight engagement of the valve body 47 with the inner face of the bore of the sleeve 40, a suitable O-ring 98 is provided.

The valve body includes a chamber formed with a conical (bottom) end from which extends a bore 52. The chamber encloses a valve 50 in the form of a stainless steel ball. The valve ball, of a diameter slightly less than that of the bore of the valve body, is adapted to engage the valve seat when moved inwardly, in a line engagement or contact. The length of the valve body bore or chamber is so chosen that the ball will have a slight movement between the wafer 64 and the valve seat.

In practice, the bushing 16 and the sleeves 21 and 40 will usually be made of steel; the screws 43 and 62, the valve body 47 and the wafer 64 will be made of an aluminum alloy known in the United States of America and Canada as Duralinium. Such alloy is soluble in hydrochloric acid, but not in acetic acid.

Should it be found desirable to remove the bushing and both sleeves so as to increase the ultimate size of passage to the diameter of the hole through the casing 12, these three parts will also be made of the aluminum alloy.

After final assembly of the duct-forming devices, the bore of the plug 43 is lled with an acid-soluble compound as aforesaid.

The diaphragms 61 and 57 are so chosen for thickness having regard to the metals used and the diameters of the bores intended to be closed to uid pressure within the casing orl liner 12, that they will withstand all pressures in excess of that required to shear away the shearing wire 1D0-100A on the sleeves 21 and 40, respectively, in order that cement may be pumped up into the annular space between the casing or liner 12 and the wall of the bore hole to a level such as to surroundl the extended sleeves 21 and 40 without puncturing the diaphragms. Such diaphragms of Yzinc and magnesium are removed 'by acetic acid, as aforesaid, without affecting the Duralinium parts, the magnesium diaphragm being dissolved and the zinc .diaphragm being eroded or attached by electrolytic action.

The `preferred method of operation will now be described. The casing or linear 12, with duct-forming devices in place, is lowered into the bore hole 10 until it engages the bottom. The devices 15 are now opposite the strata 14 to be tapped. A volume of sealingcement such 4as will lbe required to lill the annular space to the height necessary to surround or encase the sleeves of the devices when the sleeves have been moved outwardly against the wall of the bore hole, is pumped into the casing or liner 12. On top of the cement and separated by a cementing plug, is pumped acetic acid, in a volume such as to later submerge all ofthe duct-forming devices when the -acid reaches near the bottom of the casing. On top of the acetic acid and separated preferably by another cementing plug, is pumped a displacement fluid until the cement is -displaced to casing bottom. Continued pumping will force the cement through the bottom of the casing and up into the annular space. At this time, that is, when all of the cement has been raised into the annular space, the acetic acid submerges all of the devices 15 and the first mentioned cementing plug is seated below all of the devices 15. Further continued pumping creates the pressure build-up above the seated rst cement plug of about 1500 to 1800 pounds per square inch which is necessary to shear the wires 100-100A, causing the sleeves to move outwardly through the liquid cement, the plug 59 coming into engagement with the wall of the bore hole, the acetic acid filling the annular space within the bushing and the outer sleeve 21 and coming into contact with the exposed rear end of the plug 45 and quickly dissolving it. This plug takes the shock or hydraulic hammer off of the diaphragm 57 when the sleeve 40 stops travelling after the shear wires give way. The action of the locking rings 32 and 32A prevents any inward movement of the sleeves 21 and 40.

The cement will be chosen so as to have approximately a three-hour initial setting period. The strength of the acetic acid and the thickness of the zinc diaphragm 57 are so selected as to require an appreciably greater length of time than three hours before the diaphragm (which forms an anode) becomes eroded or weakened sufficiently by the action of the acetic acid to be hydraulically punctured by the fluid pressure within the casing. For instance, in a SOOO-foot well, at about 120 F. bottom hole temperature, I found that a .024-inch zinc diaghragm, covering a .12S-inch hole, punctured in about eight hours after erosion under the fluid pressure of the displacement lluid (preferably oil) lying above the acetic acid. We use a 10% to 12% acetic acid. The pressure of a 500G-foot lhead of iluid is about 1700 to 2200 pounds per square inch. On the other hand, without weakening the zinc diaphragm by acetic acid action, as described above, I estimate that it would require about 30,000 pounds per square inch to puncture the diaphragm. For deeper wells (deeper than 5000 feet) because of a higher lluid column exerting greater pressure on the diaphragm, the thickness of the diaphragm will be increased so that approximately the same eight-hour period will still be required before the diaphragm has been punctured.

After a period of eight hours, the cement has so hardened that it is safe for the acetic acid to flow into the valve chamber and through the wafer 64, to attack the more readily soluble magnesium diaphragm 61 and the magnesium plug 59.

When the plug 59 has been removed or dissolved (which is very rapid) the acetic acid removes or dissolves the thin lm of cement (1/16 to 1&4 of an inch thick) which laboratory tests show penetrates the wall ofthe bore hole, whether in sand or limestone. The removal of this thin film takes place while the cement is becoming sufficiently hard for the casing to be landed or anchored at the surface of the well and the conventional head equipment installed on the casing. The well is thus being treated while work of anging down proceeds at the well surface.

As will be clearly shown, the check valve 50 has a delinite function. The procedure is to displace all the acid in the casing into the formation while the second cementing plug cornes to rest on a thin ring (seat) previously installed when putting `in the casing, and which ring is above the devices 15. The casing can then be filled with oil by circulating it in through tubing (chasing out any other uids which may be there, as mud etc.), then the tubingl can be set down or rested on the second cement plug (now on the thin ring) and shear the ring by force from its shear pins (not shown) and push it to bottom.

`The well is now full of oil (ready for treatment) and even though it has been treated with aceticacid, it cannot ow even if the reservoir pressure is great enough, because of the ball check valve. This is an important function of the check valveallowing the changeover of heavy fluids to light (oil) without flowing or loss of control until the tubing is inserted in the well and in place. Hydrochloric acid can next be pumped to the well bottom to cover the devices 15, and eat them out (that is the aluminum parts) while acidizing the well. The inside (casing) side of the bushing 16, FIGURE 2, presents a valve seat edge (101) which allows for perfect seating by plastic 1 inch balls dropped in the injection media (stimulation uids) at intervals to close those devices through which stimulation has already taken place and allow others to be treated opposite less permeable bands of the formation. This allows for precision seating of sealer spheres not possible in jagged orifices made by gun perforating or jet shaped charge perforating.

When the well is so prepared, the introduction of more hydrochloric acid into the formation (preferably 15% more or less) will rapidly dissolve any possible remaining parts or components of the device, other than the sleeves and the valve proper or ball S0 (unless it is also Duralinium). This check valve no longer functions since its aluminum seat has been eaten away. Thus there is provided a duct or passage of a diameter equal to the inside diameter of the inner sleeve 40. If desired, the sleeves may be made of a material dissolvable in hydrochloric acid so as to give larger openings. The well will now be ready for production in the conventional manner of swabbing down the fluid in the well.

As already stated, the zinc diaphragm is attacked by electrolytic action. The steel parts and the casing act as the cathode, while the zinc diaphragm acts as an anode, the acetic acid constituting the electrolyte.

What I claim is:

1. In apparatus for use in a bore hole traversing porous strata to be tapped, a duct-forming device adapted to be supported by a bore hole casing comprising a tubular bushing mountable in an opening in the wall of the casing, a sleeve slidable outwardly in said bushing, releasable means on said sleeve resisting outward movement of said sleeve in said bushing, said means including a curved length of wire of rectangular cross section ixedly carried by the outer surface of said sleeve and abutting a portion of said bushing adapted to be sheared by pressure applied to the inner portion of the wire as said sleeve is moved axially outwardly in said bushing, means positioned between said sleeve and said bushing preventing inward movement of said sleeve in said bushing, members in said sleeve having aligned bores therein and plugs in said bore initially preventing passage of fluid therethrough, said plugs being dissolvable in acid to define a passage at least through part of said device, and at least one rangible diaphragm closing the passage and adapted to be ruptured by fluid pressure within the casing after said sleeve has moved outwardly.

2. In apparatus for use in a bore hole traversing porous strata to be tapped, a duct-forming device adapted to be supported by a bore hole casing comprising a tubular bushing mountable in an opening in the wall of the casing, a sleeve slidable outwardly in said bushing, releasable means on said sleeve resisting the outward movement of said sleeve in said bushing, means positioned between said sleeve and said bushing preventing inward movement of said sleeve in said bushing, members in said sleeve having aligned bores therein and plugs in said bores initially preventing passage of iluid therethrough, said plugs being dissolvahle in acid to delinea passage at least through part of said device, a one-way check valve in said sleeve 2 to prevent flow of uid toward the inner end of said sleeve, and a pair of frangible diaphragms one positioned on either side of said check valve closing said passage, said diaphragms being of dissimilar metals and dissimilar to that of said sleeve so as to render said diaphragms suc- 25 cessively responsive to electrolytic action when al suitable References Cited by the Examiner `UNITED STATES PATENTS 1,992,424 2/ 1935 Halliburton 166-151 2,460,561 2/ 1949 Winkelmann 166-225 2,707,997 5/1955 Zandmer et al. 166-100 2,708,000 5/1955 Zandmer 166-100 2,775,304 12/1956 Zandmer 166--100 2,855,049y 10/1958` Zandmer 166-100 OTHER REFERENCES German Printed Application No. Z3255 VI/ 5a;

Coburn, R. W.: The Permeator, in the Oil and-Gas' Journal, vol. 57, No. 44, 10/1959, pp. 100 to 105.

CHARLES E. OCONNELL, Primary Examiner.

BENJAMIN BENDETT, Examiner.

D. C. BLOCK, T. A. ZALENSKI,

Assistant Examiners. 

1. IN APPARATUS FOR USE IN A BORE HOLE TRAVERSING POROUS STRATA TO BE TAPPED, A DUCT-FORMING DEVICE ADAPTED TO BE SUPPORTED BY A BORE HOLE CASING COMPRISING A TUBULAR BUSHING MOUNTABLE IN AN OPENING IN THE WALL OF THE CASING, A SLEEVE SLIDABLE OUTWARDLY IN SAID BUSHING, RELEASABLE MEANS ON SAID SLEEVE RESISTING OUTWARD MOVEMENT OF SAID SLEEVE IN SAID BUSHING, SAID MEANS INCLUDING A CURVED LENGTH OF WIRE OF RECTANGULAR CROSS SECTION FIXEDLY CARRIED BY THE OUTER SURFACE OF SAID SLEEVE AND ABUTTING A PORTION OF SAID BUSHING ADAPTED TO BE SHEARED BY PRESSURE APPLIED TO THE INNER PORTION OF THE WIRE AS SAID SLEEVE IS MOVED AXIALLY OUTWARDLY IN SAID BUSHING, MEANS POSITIONED BETWEEN SAID SLEEVE AND SAID BUSHING PREVENTING INWARD MOVEMENT OF SAID SLEEVE IN SAID BUSHING, MEMBERS IN SAID SLEEVE HAVING ALIGNED BORES THEREIN AND PLUGS IN SAID BORE INITIALLY PREVENTING PASSAGE OF FLUID THERETHROUGH, SAID PLUGS BEING DISSOLVABLE IN ACID TO DEFINE A PASSAGE AT LEAST THROUGH PART OF SAID DEVICE, AND AT LEAST ONE FRANGIBLE DIAPHRAGM CLOSING THE PASSAGE AND ADAPTED TO BE RUPTURED BY FLUID PRESSURE WITHIN THE CASING AFTER SAID SLEEVE HAS MOVED OUTWARDLY. 